The present invention relates to a pneumatic tire, more particularly to an asymmetrical tread pattern which can be employed in both of right tire and left tire to improve off-road grip during high-speed running and thus which is suitable for racing use such as rally, dirt trial and the like.
In the laid-open Japanese patent application JP-A-11-268506 (corresponding to EP 0943464 A2), a pair of asymmetrical tread patterns specialized for right tire and left tire to improve off-road grip were proposed by the present inventor.
Under actual conditions in rally, dirt trial or the like, there are many occasions such that the tire is punctured, and a tire on one side of the vehicle wears more than a tire on the other side. In the former case, the vehicle must be equipped with two spares for right and left tires. In the later case, if the worn tire and the less worn tire are exchanged in their positions to even the wear, various performances get out of order due to the directional tread patterns.
It is therefore, an object of the present invention to provide a pneumatic tire which can be used on both sides of a vehicle and which has a tread pattern being capable of improving off-load grip such as traction, braking and side grip.
According to the present invention, a pneumatic tire comprises
a tread portion provided with a block pattern being asymmetric about the tire equator, the tread portion having an inside tread edge and an outside tread edge to be placed on the inside and outside of a vehicle, respectively,
outside lateral grooves extending from the outside tread edge to a tread center region, each having a groove center line X0 inclined towards one direction with respect to the tire circumferential direction at an angle xcex80 of from 40 to 60 degrees with respect to the tire circumferential direction,
inside lateral grooves extending from the inside tread edge to the tread center region, each having a groove center line X5 inclined at an angle xcex85 of from 70 to 100 degrees with respect to the tire circumferential direction,
each portion between the circumferentially adjacent outside lateral grooves divided into outside blocks by outside connecting grooves extending thereacross, the outside connecting grooves comprising a first groove, a second groove, a third groove and a fourth groove arranged in this order from the outside tread edge toward the inside tread edge,
the first outside connecting groove having a first groove center line X1, the second outside connecting groove having a second groove center line X2, the third outside connecting groove having a third groove center line X3, the fourth outside connecting groove having a fourth groove center line X4, the first to fourth groove center lines X1 to X4 inclined reversely to the groove center lines X0 of the outside lateral grooves with respect to the tire circumferential direction, and the inclination angles xcex81 to xcex84 of the first to fourth groove center lines X1 to X4 with respect to the tire circumferential direction being in a range of from 20 to 50 degrees and being different from each other.
An embodiment of the present invention will now be described in detail in conjunction with the accompanying drawings.